Digital Camera Sensor Resolution and Print Sizes

After a presentation to the 4th annual Western North Carolina Foto Fest in Montreat, NC, in September 2013, a couple participants asked me to post my two slides showing the resolutions of digital camera sensors, and effect of resolution on print sizes.

The first slide is reproduced here:

Typical Image Sizes in Pixels

Typical Image Sizes in Pixels

As you can see, a 1.0 megapixel (mp) camera has more resolution than the old NTSC television and more than most PC displays used to have. You might be surprised that a 3.0 mp sensor has more resolution than HDTV! Even more shocking, perhaps, is that the incredible iPad with Retina display has a resolution of 2048×1536 pixels—-exactly what you could capture with a 3.0 mp camera.

So what in the world do we need a 12 mp or 24 mp, or goodness knows, a 36 mp sensor for? That’s where the second slide comes in:

Print Sizes at 240 dpi

Print Sizes at 240 dpi

This chart shows the native print sizes you can make at 240 dpi from the various digital camera sensor resolutions. (Note: I’m not suggesting that you always print at 240 dpi, but that resolution was chosen as a constant to make a comparison. Selecting the appropriate print resolution is a topic unto itself.)

At 240 dpi, the 3.0 mp camera can only produce a print of about 6 1/2 x 8 1/2 inches before you have to upres the file. When you upres a file in post-processing, the software has to make up additional pixels based on adjacent pixels.

Depending on your camera’s sensor, your post-processing software, and the content of your image, you can sometimes upsample (upres) by 50-to-100%. In other words, you can sometimes almost double the pixels before it becomes noticeable. Other times, even a slight upsampling will show as undesirable artifacts in your final image. (You guessed it; this is another topic unto itself.)

As the chart shows, if you have a 13-inch desktop printer, you can print an image from a 12 mp camera at 240 dpi without any interpolation.

Higher resolution cameras allow you to make bigger prints at the same resolution. This chart shows that a 36 mp camera, like the Nikon D800E, will yield a 20 1/2 x 30 1/2 inch print at that same 240 dpi.

So while even a 6 mp camera has more resolution than almost any display (my 30″ NEC 3090WQXi display’s resolution is 2560 x 1600), more pixels will translate into larger possible prints. On the other hand, even a 3 mp camera will provide more than enough resolution for e-mailing, social media, HDTV slide shows, or cell phones and tablets.

Of course there are many other advantages to higher resolution digital camera sensors than just print size, and these can show up even in small prints. But that, too, is a topic for another post.

©2013 Tom Vadnais Photography. All Rights Reserved.

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